This invention relates to a method for the repair of the outer layer of the submarine flexible lines which are normally used to carry away the oil produced by a well. Flexible lines are subject to frequent damage, for example, due to abrasion by contact with the structure of an off-shore platform.
The oil produced by submarine oil wells equipped with wet christmas trees usually flows away to a processing unit at the surface, by means of special flexible pipings which comprises several layers of diverse functions. The outer layer is made of highly resistant synthetic fibre, the function of which is to protect from corrosion the inner layer of the steel mail or mesh that makes the pipe resistant to tension and to pressure (crushing). The segment of the flexible piping that brings the oil from the bottom of the sea to the unit at the surface is called a "riser" by the experts in the art of submarine oil wells.
When in operation, the coating of the risers frequently becomes damaged by abrasion upon contact with the structural parts of the processing unit at the surface, as result of operational conditions. When the damage affects the inner layer of the steel mesh or mail, the structure becomes exposed to corrosion, thus weakening the flexive piping or rendering it useless.
When a damaged region is detected along the flexible piping, the process of moving it mechanically is adopted immediately.
Next the repair is performed on the exposed metallic layer applying anticorrosive adhesive tapes and putting on them new layers of filamentary tape for reinforcement.
This repair method, commonly used in this kind of damage, has as a deficiency fact that the filamentary adhesive tape placed there as protection has a low resistance to abrasion and to cutting and this may cause a new occurrence of failure within a short period of time. The method of applying it, by means of divers, is slow and lengthy due to the limited autonomy of the diver, thus requiring several diving operations.